Dermatology Flashcards
What are the 4 layers of the skin from superficial to deep?
Epidermis
Basement Membrane Zone
Dermis
Subcutaneous layer
What are the 4 layers of the epidermis from superficial to deep?
Keratin layer
Granular layer
Prickle Cell layer
Basal layer
What do keratinocytes do?
Secrete a variety of cytokines in response to tissue injury or disease
In what layer are melanocytes found in?
Basal layer
Where does the epidermis originate from?
Ectoderm
What are the downward projections into the dermis from the epidermis called?
Rete Ridges
What are the 2 components of the epidermal cytoskeleton?
Keratin filaments
Desmosomal proteins
Which epidermal layer creates the semi-permeable skin barrier
Granular layer
What is the name of the skin cells which lose their nucleus in order to become surrounded by an inpermeable, protein envelope?
Stratum corneum cells
What types of immune molecules are involved in the innate immune system of the skin?
Netrophils, macrophages and keratinocytes
What can a deficiency in the skin’s innate immune system cause?
Atopic eczema
What is the role of melanocytes in the skin?
UV protection
Where are Merkel cells found?
Basal layer
What is the role of Merkel cells?
play a role in sensation esp. on fingertips and in the oral cavity
What are Langerhans cells?
Dendritic cells in the supra-basal layer; antigen presenting cells
What is the other name for the Basement Membrane Zone?
Dermo-epidermal junction (DEJ)
What does the basement membrane zone consist of?
Many types of collagen
Hemidesmosomal proteins
Integrins
Laminin
What is the role of the DEJ?
keeps the dermis and epidermis firmly attached
What can protein deficiencies in the DEJ cause?
Fragility of skin and a number of blistering diseases
Where does the dermis originate from?
Mesoderm
What does the dermis contain?
Blood, lymphatics, nerves, muscle
What is the dermis made of?
Collagen and Elastin in a ground substance
Where is the only surface Eccrine sweat glands are not found?
Mucosal surfaces
Where are the apocrine sweat glands found?
Axillae, anogential area, and scalp
What is the function of the sebaceous glands?
Secrete sebum (grease) onto the skin surface via the hair follicle - after puberty
How does hair form?
Downgrowth of epidermal keratinocytes into the dermis
What are the different parts of a hair shaft?
Inner and outer root sheaths, cortex, medulla
What are the 3 types of hair?
Terminal - scalp, beard, pubic
Vellus - fine downy hair on women’s faces and prepubescent children
Lanugo - Soft hair covering newborns (esp those premature)
What does the lower portion of the hair follicle consist of?
Expanded bulb (contains melanocytes), which surrounds a dermal papilla
What are the 3 stages of the hair growth cycle?
Anagen - growth phase
Catagen - involution phase
Telogen - Shedding phase
What causes hair to go grey?
decreased tyrosinase activity is hair bulb melanocytes
What causes hair to go white?
Total loss of melanocytes
What are nails?
Tough plates of hardened keratin
Where does nail growth arise from?
Nail matrix
What constitutes the subcutaneous layer?
Adipose tissue, blood vessels and nerves
Where do melanocytes originate from?
Neural crest
At what stage does a foetus have fully developed skin and hairs?
26 weeks
Histologically how is the epidermis described?
Stratified squamous epithelium
Histologically what is the basal layer made up of?
Once cell thick cuboidal cells
Intermediate filaments
What is the prickle cell made up of?
Polyhedral cells
Desmosomes
Keratohyalin granules
What does the keratin layer consist of?
Corneocytes
Keratin
Filaggrin
What is special about the cells of the oral mucosa?
Keratinised to deal with friction and pressure
What is special about the cells of the occular mucosa?
Lacrimal glands
Eye lashes
Sebaceous glands
Where do Melanocytes migrate from and to?
From the neural crest to the epidermis
What are melanocytes and where are they found?
Pigment-producing dendritic cells
In and above the basal layer
What colour is Eumelanin?
Brown or black
What colour is phaeomelanin?
Red/yellow
Where do Langerhans cells originate from?
Mesenchymal cells (bone marrow)
Where are Langerhan’s cells found?
Prickle cell layer (also dermis and lymph nodes)
How are Langerhans cells characterised histologically?
By Birbeck granules (they look like sports raquets)
Where are Merkel cells found?
Basal layer (between keratinocytes and nerve fibres)
What type of cell are Merkel cells?
Mechanoreceptors
What is dermographism?
Skin becomes raised and inflamed when stroked or scratched etc.
What causes dermographism (dermatographic urticarial)
Mast cells release histamines in the absence of antigens, due to their weak membranes
What can the sun do to the skin on a microscopic level?
Solar elastosis - elastin filaments break up and cause the skin to wrinkle
What receptors in the skin sense pressure changes?
Pacinian Corpuscles
What receptors in the skin sense vibrational changes?
Meissners Corpuscles
Under a microscope what do Pacinian Corpuscles look like?
sliced onion
Sebaceous glands are dormant at birth, when do they become active?
Puberty
What do sebaceous glands do?
Produce sebum to control moisture loss and to protect from bacterial and fungal infection
What causes acne?
Increased sebum production, blocked ducts and bacterial activity
Where would you find apocrine sweat glands?
Axillae and perineum
What do apocrine sweat glands do?
Produce an oily fluid which produces an odour after bacterial decomposition
What are apocrine sweat glands dependent on?
Androgens
Where do you find Eccrine sweat glands?
Whole skin surface; esp. palms, soles and axillae
What is the nerve supply to the eccrine sweat glands?
Sympathetic cholinergic nerve
What is the role of the eccrine glands?
Ultrafiltration of fluids
cooling by evaporation
Moistening palms and soles to aid grip
Give 2 examples of conditions considered as acute skin failure.
Toxic Epidermal necrolysis
Erythroderma
What to metabolic processes is the skin heavily involved in?
Vitamin D metabolism - Uv absorbed in skin helps in vit D metabolism
Thyroid Hormone metabolism - is 1 located of where T4 is converted to T4
What cells are important in the skin’s immune function?
Langerhan’s cells
T-Cells
What is impetigo?
A highly infectious skin disease which is most common in children
How does impetigo present clinically?
Weeping, exudative areas with a honey-coloured surface crust
How is impetigo spread?
Direct contact
What organisms can cause impetigo?
Staph
Group A beta-haemolytic strep
If impetigo is caused by a Staph infection, how is it treated?
Oral antibiotics (7-10 days) Flucloxacillin 500mg 4xdaily
If impetigo is caused by a Strep infection, how is it treated?
Phenoxymethylpenicillin 500mg 4xdaily (7-10 days)
If impetigo doesn’t respond to initial treatment what should then be done?
Nasal swabs taken
Nasal mupiocin 3xdaily (1 week) to eradicate nasal carriage
Staph infections can rarely release exfoliating toxins which act high up in the epidermal layer. What effects does toxin A produce if it is released?
Blistering at the infection site - bullous impetigo
Staph infections can rarely release exfoliating toxins which act high up in the epidermal layer. What effects does toxin B produce if it is released?
Staph Scalded Skin Syndrome (SSSS) - more widespread blistering
What groups are more at risk of developing SSSS?
Children
Immunosuppressed adults
Adults with renal disease
How are toxic infections released from Staph infections treated?
Flucloxacillin (with supportive care)
What is cellulitis?
A hot, tender area of confluent erythema due to deep subcut. infection (occasional blistering)
Where does cellultis often affect?
Lower leg (upward spreading)
What general symptoms will a patient with cellulitis have?
Generally unwell with a fever
What causes cellulitis?
Beta haemolytic strep or staph (rare)
Immunosuppressed/diabetic patients may develop gram -ve or anaerobic infection
How is cellulitis conformed/organism identified?
Serology
How is cellulitis treated?
Phenoxymethylpenicillin (or erythromicin) and flucloxacillin 500mg 4xdaily
What is ecthyma?
Chronic, well-demarcated, deeply ulcerative lesions (sometimes with an exudative crust)
What causes ecthyma
Strep or Staph infection
Ecthyma is rare in the UK, but what groups of patients may develop it?
IVDUs and HIV patients
What is the treatment for ecthyma?
Erythromicin PO 500mg 4xdaily for 7-10 days
What is erythrasma?
Orange-brown flexural rash - often seen in axillae or toe web spaces
What causes erythrasma?
Corynebacterium minutissimum
How does erythrasma appear under Wood’s light?
Coral pink fluorescence
How is erythrasma treated?
Erythromicin PO 500mg 4xdaily for 7-10 days
What is folliculitis and how does it present?
Inflammation of the hair follicle which presents with itchy, tender papules
What is the commonest causative organism of folliculitis?
Staph aureus
What is the treatment for folliculitis?
topical antiseptics and either topical or oral antibiotics
What are furuncles?
(Boils) are deep seated infections of the skin which present as painful, red swellings
What causes furuncles?
Staph infection
What should be done to ensure MRSA is not the cause of a furuncle?
Swabs for antibiotic sensitivities
How are furuncles treated?
Erythromicin 500mg 4xdaily for 10-14 days
Antiseptics (chlorhexidine) can be useful as prophylaxis
What is hidradentis suppurativa?
A painful, discharging, chronic inflammation in areas rich in apocrine glands of which there is no known cause
How is hidradentis suppurativa treated?
Weight loss, antibiotics and oral retinoids
What is pitted keratolysis?
A superficial infection of the horny layer of the skin caused by a corynebacterium
How does pitted keratolysis present?
On soles of feet with numerous, small, punched out lesions on a macerated (prune-like) skin
How is pitted keratolysis treated?
Topical antibiotics and anti-sweating lotions
How does leprosy present?
Rare in UK
Usually involves skin and the features depend on an individuals immune response to Mycobacterium leprae
What skin manifestations of TB are there?
Lupus vulgaris
Tuberculosis verrucoa cutis
Scrofuloderma
The tuberculides
What is viral exanthem?
The commonest type of viral-induced rash which presents as a widespread nonspecific erythamatous maculopapular rash.
What causes viral exanthem?
Circulating immune complexes of antibody + viral antigen localising to dermal blood vessels
What is Slapped Cheek Syndrome, and what causes it?
A rash across the face which can occur for weeks-months which is caused by Human Erythrovirus B19
Patient is generally well throughout and after the facial rash has cleared a lacy, macular rash appears on the body
Most people are affected by HSV1 in childhood and the majority have subclinical infection. If not however, how does this present?
Clusters of painful blisters on the face (esp around the mouth)
If HSV1 reccurs, how does it present?
Usually as cold sores
What does HSV2 infection typically cause?
Genital herpes
How is HSV infection treated?
Oral aciclovir 500mg 2xdaily for 5 days
Cold sores can be treated with topical aciclovir creams
What 2 diseases does varicella zoster virus cause?
Chicken pox - Varicella component
Shingles - Zoster componenet
How does chicken pox present?
Generlised itchy rash and fever
What complications can arise from chicken pox?
secondary infection pneumonia haemorrhagic rash scarring encephalitis (brain tissue swelling)
How is chicken pox treated?
It isn’t usually - self limiting process
Infection = immunity in most cases
What causes shingles?
Reactivation of the virus, usually in older age in a dermatomal pattern
How does shingles present?
Preceded by a tingling sensation or pain
This is followed by a painful, tender, blistering erruption which occur in crops, become pustular and then crust over
How long does a shingles rash typically last for?
2-4 weeks
What complications can arise from shingles?
Severe, persistant pain
Others depending on the dermatome affected
How is shingles treated?
Analgesia and antibiotics (if secondary bacterial infection)
Valaciclovir1g or famciclovir 250mg 3xdaily for 7days (shortens attacks)
What does HPV cause relating to the skin?
Viral Warts
What are common HPV warts?
Papular lesions with a course, roughened surface often seen on the hands and feet.
They have small black dots (bleeding points)
How do HPV common warts spread?
Direct contact
What is another name for plantar warts caused by HPV?
Verrucae
What are plane warts?
Less common lesions caused by only certain types of HPV. Are very small, flesh coloured/pigmented and flat topped.
Where are plane warts typically found?
Face or backs of hands - usually in multiples
How are warts caused by HPV treated?
almost always resolve spontaneously
Topical keratolytic agents can speed up the healing process
Cryotherapy may also be helpful but it does have side effects
What is molluscum contagiosum?
A common cutaneous infection in childhood causing multiple small translucent papules which are solid to touch
What causes molluscum contagiosum?
The pox virus
How is molluscum contagiosum spread and how long does infection last?
Direct contact
6-12 months
What is orf?
A pox virus disease of sheep which can be spread to humans via direct contact
How does orf present?
1-2cm reddish papule with a surrounding erythema which usually becomes pustular
What is tinea corporis?
A dermatophyte fungal infection of the body
How does tinea corporis present clinically?
Asymmetrical scaly patches with central clearing and an advancing, scaly raised edge.
What is tinea faciel?
A dermatophyte fungal infection of the face
How does tinea faciel present?
Often occurs after topical steroid use
Erythematous, slightly scaly lesions
Itchy after sun exposure
What is tinea cruris?
A dermatophyte fungal infection of the groin
How does tinea cruris present?
Well-demarcated, red plaques with arc like borders, extending down from the upper thighs
What is tinea pedis?
A dermatophyte fungal infection of the feet
How does tinea pedis present?
Infection mainly in the toe clefts with white, macerated and fissured lesions
What is tinea manuum?
A dermatophyte fungal infection of the hands
How does tinea manuum present?
A diffuse, erythematous scaling of the palms and backs of hands
Variable skin peeling and thickening
What is tinea capitis?
A dermatophyte fungal infection of the scalp
How does tinea capitis present?
From a mild diffuse scaling with no hair loss, to scaly patches with associated alopecia.
May present with a few pustules with exudate
What is tinea unguium?
A dermatophyte fungal infection of the nails
How does tinea unguium present?
An asymmetrical discoloration of 1 or more nails
Nail plate appears thickened and a crumbly white material appears under it
What is tinea incognito?
A fungal skin infection modified by topical steroid use
How does tinea incognito present?
Variable - non-specific erythema or a few reddish nodules with a little scaling. Rash improves with steroids but gets and spreads when treatment is stopped
What is the treatment for all tinea infections?
Body of flexures = topical antifungals Widespread = oral antifungals Toenails Itraconazole (antifungal) for 3-6 months
What is Candida albicans?
An opportunistic yeast that thrives in warm and moist environments
How would a candida albicans infection present?
A superficial white/creamy psuedomembranous plaque which can be scraped off leaving raw areas underneath.
Satellite lesions may also be found
How is a candida albicans infection treated?
Topical antifungal creams
Nail infections need systemic antifungal therapy
What is pityriasis versicolour?
An overgrowth of the normal bacterial skin flora or pityrosporum
How does pityriasis versicolour present?
In white people - reddish-brown scaly lesions on the trunk
In black people - macular areas of hypopigmentation
How is pityriasis versiolour treated?
Slenium sulphide or 2% ketoconazole shampoo or topical imidazole cream
What is seborrhoeic eczema?
A pityrosporum folliculitis
How does seborrhoeic eczema present?
Small itchy papules on the upper back, centered on the hair follicles (common in young adult males)
How is seborrhoeic eczema treated?
ketoconazole shampoo or topical imidazole cream
What is scabies?
An intensely itchy rash caused by the sarccoptes scabies mite
How does scabies present?
Itchy red papules anywhere on the skin
Sometimes liner or curved burrows can be seen
Itch is usually worse at night
What complications can arise from scabies?
Excoriations
Secondary bacterial infections
How is a diagnosis of scabies confirmed?
Skin scrapings and examining a potassium hydroxide preparation by microscopy for the mites and/or eggs
How is scabies treated?
Topical scabicide is applied and washed off after 10 hours (all skin below the neck)
In under 2s treat head and neck aswell
All close contacts should be treated even if they are asymptommatic
How does crusted (Norwegian) scabies differ from regular scabies?
Occurs in immunospressed people where huge numbers of mites are carried. It is not always itchy but is extremely effective.
How does Norwegian scabies present?
Hyperkeratotic crusted lesions
May progress to widespread erythema with irregular crusted plaques.
How is Norwegian scabies treated?
Careful barrier nursing
Repeated applications of a scabicide
Oral invermectin
What are lice?
Blood sucking ectoparasites that can affect humans in 3 ways.
How do headlice present?
Itch
Scalp excoriations
Papules on the neck
How are headlice diagnosed?
The presence of eggs stuck to the hair shaft
How are headlice treated?
eradication difficult due to non-compliance and resistance
Malathion, carbaryl and phenothin are the most commonly used agents (insecticides)
How do body lice present clinically?
Itch
Excoriations
post-inflammatory hyperpigmentation of the skin
Infestation of poverty and neglect
How should body lice be treated?
malathion/permethrin for patient and high temp washing and drying of clothing
How do pubic lice present?
Itching esp. at night
How are pubic lice treated?
Malathion, carbaryl and phenothin are the most commonly used agents (insecticides)
How do arthropod-borne diseases (insect bites) preset?
itchy urticated lesions, often grouped in clusters
How can eczema present histologically?
A collection of fluid in the epidermis between keratinocytes (spongiosis) and an upper dermal peri-vascular infiltrate of lymphohistiocytic cells
How can chronic eczema present histologically?
marked thickening of the epidermis (acanthosis)
What is the prevalence of atopic eczema?
Common - upto 5% of UK
10-20% children
What is the initial pathophysiological process of atopic eczema?
Selective activation of Th2CD4 lymphocytes driving the inflammatory processes
What cells predominate the chronic phase of atopic eczema?
Th0 and Th1
What immunoglobulin is raised in 80% of patients with atopic eczema?
IgE
What is fillagrin?
An epidermal barrier protein
How is it thought that having a mutation in the filaggrin gene can predispose an individual to atopic eczema?
Mutations can cause ichthyosis vulgaris which can predispose Caucasians to atopic eczema.
What things may exacerbate atopic eczema?
Infections Lack of infant infection Chemicals/detergents Teething, stress, anxiety Cat + dog fur Foods and house mites
How does atoptic eczema most commonly present?
Itchy, erythematous, scaly patches esp. in flexures
Where does atopic eczema start in infants?
Head and face
What differences may acute lesions in atopic eczema show?
Weeping or exudate and small v present?esicles
What ca a chronic scratching in atopic eczema lead to?
Lichenification with exaggerated skin margins
In patients with pigmented skin, how would atopic eczema present?
Extensor involvement
May be papular or follicular in nature
Post-inflammatiry hyper or hypo pigmentation may occur and this is usually very slow to resolve
Other than the itchy lesions associated with atopic eczema, how else may it affect the skin?
Upper arm and thigh skin may feel roughened due to follicular hyperkeratosis
Palms have prominant skin creases
May be a dry fish-like scaling on lower legs (ichthyosis vulgaris)
If a patient with atopic eczema gets a secondary infection on some lesions, what is the causative organism most likely to be?
Staph aureus
How would a secondary infection of staph aureus to atopic eczema present?
Crusted, weeping, impetigo-like lesions
Why are cutaneous viral infections widespread when they infect atopic eczema lesions?
Due to sratching
If HSV infects areas of atopic eczema, what is this condition called?
eczema herpeticum
How does eczema herpeticum present?
Multiple, small blisters or “punched-out” crusted lesions associated with malaise and pyrexia
How is eczema herpeticum treated?
Rapid oral or IV aciclovir
What signs can appear in the eyes of somebody with atopic eczema?
Conjunctival irritation
keratoconjunctivitis
Cataract
If a child has chronic-severe atopic eczema what clinical sign may become apparent as they grow older?
Retarded growth (nothing to do with steroids!!)
How is atopic eczema diagnosed?
Clinically based on examination and history
How is the atopic part of atopic eczema diagniosed?
High serum IgE or high specific IgE to antigens
Also blood eosinophilia in 80% patients
If a patient has atopic eczema as a child, what are the chances it will spontaneously resolve before they reach their teenage years?
80-90%
What general lifestyle measures can be used to treat atopic eczema?
Avoiding irritants
Cotton clothing
Avoiding overheating
Potentially avoiding dairy and eggs in the under 1s
What is the commonly used triple therapy of topical agents used to treat atopic eczema?
Topical steroid
Frequent emolients
Bath oil and soap substitutes
What potency of steroids should be used on the face in atopic eczema?
ONLY mild steroids
What potencies of steroids may be used on the body in a patient with atopic eczema?
Mild
Moderate
Diluted potent
Potent and very potent steroids may need to be used on what body areas in atopic eczema?
Palms and soles (thicker skin)